This invention relates to an integrated injection logic (I.sup.2 L) bipolar memory cell and, more particularly, to an I.sup.2 L memory cell employing both vertical and lateral injectors.
Two basic but different types of I.sup.2 L memory cells are known. A first, described in "Superintegrated Memory Shares Functions on Diffused Islands" by S. K. Wiedmann and H. H. Berger, Electronics, Feb. 14, 1972, page 83, consists of two dual collector I.sup.2 L cells sharing the same injector. The base of each is cross-connected to a collector of the other cell. The remaining collector of each cell serves as a read/write-input/output terminal. The layout of this circuit in a word-organized array exhibits certain disadvantages. First, the P-type emitter (injector) occupies space which, in the long run, reduces density. Secondly, the source of voltage applied to the injector has to be applied to all P-type emitters of one word by means of a metal strip deposited during a second metallization step.
A second type of I.sup.2 L cell is described in "Injection-Coupled Memory: A High Density Static Bipolar Memory" by S. K. Wiedmann, IEEE Journal of Solid State Circuits, Vol. SC-8, No. 5, October, 1973, page 332. The cell consists of two single collector I.sup.2 L cells sharing one injector and having one exclusive injector for read/write-input/output functions. Thus, a total of three injectors per cell is required. To avoid the problem of dual metallization, the layout of this cell is modified so that the read/write injectors are shared between adjacent cells in the same word line. This requires complicated decoding techniques due to the multiple duties of the read/write injectors.